I started out this school year teaching my oldest two together in certain subjects(health, science, history, bible, and a couple others.. Now I am seriously considering changing it to teaching them separately.
They both seem to be interested in different topics in science, my younger child is not grasping the history and it just seems like a battle to do them both at the same time now. I am seriously considering working with them both completely separate for a few months.
They are only two years apart I had hoped to keep them together, but I may be finding a completely new path with some of this. My 7 yr old is doing 1st grade work. My 5 yr old is doing K and 1st grade work.

Well I sat down while the middle child was napping (she's a little under the weather today), and figured out how to mostly do their lessons separate. It took me a little longer, but I feel like they did better that way.
I still did a couple things together, but I can see that as my oldest get's a little older, he will start to do more and more on his own. Like today he read all of his math instructions and his devotional by himself. I may go ahead and have him read all of those to me from now on..and then work with the younger one separately.
I am sure that as soon as I get this all figured out, someone will have a change or the youngest one will be ready to instruction and we will have to start from square one again! Lol

the subjects i teach apart are math and lang. arts, we all do the same science and history and bible, during the year i have the kids write down what they want to learn about in science and history and i make up unit studies during our off time(july- august, its funny a lot of them want to learn about the same things!

i have also taught them separate in all subjects, works better if the kids are older and can be independant then they can go from subject to subject (when theres more than 2 kids)

My kids are 11 months apart and two grades apart because my older is gifted. They are also very different learners. I just started combining literature this week as an expiriment. If it works, I will combine history and science next year. We shall have to see.